Why Was This Indicator Chosen?

Endangered coho salmon (Oncorhynchus kisutch) in Lagunitas Creek are good indicators of riparian habitat and hydrological conditions as well as ocean health, and provide marine-derived nutrients for aquatic and riparian communities. Decades of monitoring data covering all life stages make it possible to assess the condition and trend of coho salmon on Mt. Tam with a fairly high level of confidence.

What is Healthy?

The desired conditions for the Lagunitas Creek coho salmon populations are described in numerical targets for each life stage, as well as the critical habitat conditions that support those life stages. The National Fish and Wildlife Service (NMFS) recovery plan for this species (NMFS, 2012) lists specific goals for the number of adult spawners and redds (nests), juveniles, and smolts (young fish migrating out to sea), and the amount of woody debris in the stream.

What Are the Biggest Threats?

• Historic hydrological changes and habitat loss that have affected anadromous fish migration, increased sedimentation, and reduced the number of pools and other critical habitats
• Current hydrological changes and habitat loss including water withdrawals, drought, channel incision, and a loss of downstream floodplain connectivity
• Ocean-related factors such as over-harvesting of salmonids as well as their prey (e.g., sardines) and changes to ocean food webs related to climate change
• Potential invasive aquatic species including exotic mollusks such as New Zealand mud snail (Potamopyrgus antipodarum) and the spread of invasive Japanese knotweed (Fallopia japonica)
• The effects of climate change such as higher water temperatures, longer droughts, more intense rainfall, and disruptions in the ocean food web

What is The Current Condition?

The overall condition of Lagunitas Creek’s coho salmon is Poor. The 20-year average for adults and redds is only approximately 20 percent of the NMFS recovery goal, and smolts are only at approximately 18 percent. Numbers of juvenile coho salmon in Lagunitas Creek are low and fluctuate widely. Wood loading levels are also low.

What is the Current Trend?

Currently, we believe that coho salmon in Lagunitas Creek are experiencing No Change in habitat or population trends, except two of the three smolt year classes have shown increases over two generations. The third year class, while only increasing over one generation, reached the highest numbers seen yet.

How Sure Are We?

Overall confidence is Moderate based on the quality and the amount of data available, although there is some uncertainty about juvenile estimates and some assumptions were required to estimate wood loading and pool frequencies.

What is This Assessment Based On?

• NMFS Federal Register documents (NMFS 2012, 2015)
• National Park Service inventory and annual monitoring (Carlisle et al., 2016)
• Marin Municipal Water District annual monitoring reports (see MMWD link in References below)

What Don’t We Know?

Key information gaps include:

• The timing and magnitude of salmonid migration between streams using Passive Integrated Transponder (PIT) tag technology would provide valuable information on habitat needs during multiple life stages